Polarized Micro-Raman Spectroscopy of Ba(Mg_1/3Nb_2/3)O₃ Single Crystal Fibers

Ba(Mg 1/3 Nb 2/3 )O 3 (BMN) is a complex perovskite usually obtained in ceramic form and exhibiting remarkable microwave dielectric properties when sintered at high temperatures. The crystallographic and spectroscopic studies of this material indicate that it belongs to the trigonal P 3̄ m 1 space group, with a 1:2 ordering of Mg and Nb atoms along the [111] cubic direction. Nevertheless, studies of BMN single crystals are still lacking. In this work, we report on the first preparation and study of BMN single crystal fibers obtained by the laser heated pedestal growth (LHPG) technique. The fibers were high-quality crystalline samples grown in the 〈110〉 cubic direction and presenting facets normal to the 〈112〉 cubic axes. Polarized Raman spectra in chosen directions allow us to conclude that the crystalline structure of the fibers is the same as that of well-ordered sintered ceramics, although some regions containing a different crystalline phase were also detected. It is shown that the selection rules for the symmetry and polarization of the Raman features are fully obeyed so that the modes belonging to the totally symmetric representation (A 1g ) and to the doubly degenerate in-plane representation (E g ) could be discerned.